Integrated circuit device

ABSTRACT

An integrated circuit (IC) device includes a fin-type active region extending lengthwise in a first direction, a plurality of nanosheets overlapping each other in a second direction on a fin top surface of the fin-type active region, and a source/drain region on the fin-type active region and facing the plurality of nanosheets in the first direction. The plurality of nanosheets include a first nanosheet, which is closest to the fin top surface of the fin-type active region and has a shortest length in the first direction, from among the plurality of nanosheets. The source/drain region includes a source/drain main region and a first source/drain protruding region protruding from the source/drain main region. The first source/drain protruding region protrudes from the source/drain main region toward the first nanosheet and overlaps portions of the plurality of nanosheets in the second direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/694,706, filed Nov. 25, 2019, which claims the benefit of KoreanPatent Application No. 10-2019-0055843, filed on May 13, 2019, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND

Embodiments of the inventive concept relate to an integrated circuit(IC) device, and, more particularly, to an IC device including ahorizontal-nanosheet field-effect transistor (hNSFET).

With the downscaling of IC devices, it may be desirable to increase theintegration density of a FET on a substrate. Accordingly, an hNSFETincluding a plurality of horizontal nanosheets stacked on the samelayout region has been developed. However, when current concentratesinto a specific channel layer of a plurality of channel layers formed inthe plurality of horizontal nanosheets, even if the number of stacks ofa channel layer included in an hNSFET is increased, current (i.e., anon-current) flowing in a turn-on state of a transistor may not increasein proportion to the number of stacks of a channel layer.

SUMMARY

The inventive concept provides an integrated circuit (IC) device, whichmay reduce or minimize a deviation in the amount of current flowingthrough nanosheets in a turn-on state of a nanosheet field-effecttransistor (FET) and may improve performance in the turn-on statethereof.

According to an aspect of the inventive concept, there is provided an ICdevice including a fin-type active region extending lengthwise in afirst direction, a plurality of nanosheets overlapping each other in asecond direction on a fin top surface of the fin-type active region, anda source/drain region on the fin-type active region and facing theplurality of nanosheets in the first direction. The plurality ofnanosheets include a first nanosheet, which is closest to the fin topsurface of the fin-type active region and has a shortest length in thefirst direction, from among the plurality of nanosheets. Thesource/drain region includes a source/drain main region and a firstsource/drain protruding region protruding from the source/drain mainregion. The first source/drain protruding region protrudes from thesource/drain main region toward the first nanosheet and overlapsportions of the plurality of nanosheets in the second direction.

According to another aspect of the inventive concept, there is providedan IC device including a fin-type active region extending lengthwise ina first direction, a pair of nanosheet stacks, each of which includes aplurality of nanosheets overlapping each other in a second direction onthe fin-type active region, and a source/drain region between the pairof nanosheet stacks on the fin-type active region. The plurality ofnanosheets includes a first nanosheet, which is closest to the fin-typeactive region from among the plurality of nanosheets and has a shortestlength in the first direction. The source/drain region includes asource/drain main region, which does not overlap the pair of nanosheetstacks in the second direction, and a pair of first source/drainprotruding regions, which protrude in opposite directions from thesource/drain main region toward the first nanosheet of each of the pairof nanosheet stacks.

According to another aspect of the inventive concept, there is providedan IC device including a fin-type active region extending lengthwise ina first direction, a pair of source/drain regions located on thefin-type active region, and a plurality of nanosheets between the pairof source/drain regions and overlapping each other in a second directionon the fin-type active region. The plurality of nanosheets includes afirst nanosheet and a second nanosheet having different lengths in thefirst direction. Each of the pair of source/drain regions includes atleast one source/drain protruding region protruding toward the pluralityof nanosheets.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the inventive concept will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 illustrates a plan layout of some components of an integratedcircuit (IC) device according to some embodiments of the inventiveconcept;

FIG. 2A is a cross-sectional view taken along a line X-X′ of FIG. 1;

FIG. 2B is an enlarged cross-sectional view of a local region denoted by“X1” in FIG. 2A;

FIG. 3 is a cross-sectional view of an IC device according to someembodiments of the inventive concept, which is an enlargedcross-sectional view of a region corresponding to the partial regiondenoted by “X1” in FIG. 2A;

FIG. 4 is a cross-sectional view of an IC device according to someembodiments of the inventive concept, which is an enlargedcross-sectional view of a region corresponding to the partial regiondenoted by “X1” in FIG. 2A; and

FIGS. 5A to 5Q are cross-sectional views illustrating a process sequenceof a method of manufacturing an IC device according to some embodimentsof the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the inventive concept will now be described withreference to the accompanying drawings in which some embodiments areshown. Like reference numerals in the drawings denote like elements,and, thus, descriptions thereof will be omitted. As used herein, theterm “and/or” includes any and all combinations of one or more of theassociated listed items. It will be understood that when an element isreferred to as being “on”, “attached” to, “connected” to, “coupled”with, “contacting”, etc., another element, it can be directly on,attached to, connected to, coupled with or contacting the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being, for example, “directly on”, “directlyattached” to, “directly connected” to, “directly coupled” with or“directly contacting” another element, there are no intervening elementspresent. It is noted that aspects described with respect to oneembodiment may be incorporated in different embodiments although notspecifically described relative thereto. That is, all embodiments and/orfeatures of any embodiments can be combined in any way and/orcombination.

Some embodiments of the inventive concept stem from a realization thatin a multi-bridge channel field-effect transistor (MBCFET), current maybe concentrated in a top channel, which is close to a contact, due tosource/drain resistance an a junction profile. As a result, increasingthe number of layers in a channel stack may not result in an increase inthe on-current in proportion to the increase in the number of layers inthe stack. Some embodiments of the inventive concept may provide anintegrated circuit device including a channel structure that has reducedvariation in current flow through respective ones of a plurality ofstacked nanosheets forming a channel structure. Various techniques maybe used to reduce this variation in current flow, in accordance withdifferent embodiments of the inventive concept, including, for example,engineering the bandgap of a nanosheet that is closest to an activeregion so as to be lower than other ones of the nanosheets in the stackand/or decreasing a length of the nanosheet that is closest to theactive region relative to the other ones of the nanosheets in the stack.In other embodiments, different doping profiles and/or Ge or Ga contentprofiles may be used in the nanosheets to improve dispersion of currentthroughout the nanosheet stack.

FIG. 1 illustrates a plan layout of some components of an integratedcircuit (IC) device 100 according to some embodiments of the inventiveconcept. FIG. 2A is a cross-sectional view taken along a line X-X′ ofFIG. 1, and FIG. 2B is an enlarged cross-sectional view of a partialregion X1 in FIG. 2A.

Referring to FIGS. 1, 2A, and 2B, the IC device 100 may include aplurality of fin-type active regions FA, which protrude from a substrate102 and extend in a first horizontal direction (X direction), and aplurality of nanosheet stacks NSS, which are apart from the plurality offin-type active regions FA and face fin top surfaces FT of the pluralityof fin-type active regions FA. As used herein, the term “nanosheet”refers to a conductive structure having a cross-section that issubstantially perpendicular to a direction in which current flows. Thenanosheet may be interpreted as including nanowires.

The substrate 102 may include one or more semiconductors (e.g., silicon(Si) or germanium (Ge)) and/or one or more compound semiconductors(e.g., silicon germanium (SiGe), silicon carbide (SiC), gallium arsenide(GaAs), indium arsenide (InAs), indium gallium arsenide (InGaAs), orindium phosphide (InP)). A trench T1 may be formed in the substrate 102to define a plurality of fin-type active regions FA and may be at leastpartially filled with a device isolation film 114. The device isolationfilm 114 may include an oxide film, a nitride film, or a combinationthereof.

A plurality of gate lines 160 may be located on a plurality of fin-typeactive regions FA and extend in a second horizontal direction (Ydirection), which intersects with the first horizontal direction (Xdirection). In some embodiments, the first and second horizontaldirections may be perpendicular with respect to one another. Theplurality of nanosheet stacks NSS may be respectively located on the fintop surfaces FT of the plurality of fin-type active regions FA atintersections between the plurality of fin-type active regions FA andthe plurality of gate lines 160. The plurality of nanosheet stacks NSSmay be apart from the fin-type active regions FA and face the fin topsurfaces FT of the plurality of fin-type active regions FA. Each of theplurality of nanosheet stacks NSS may include a plurality of nanosheets(e.g., first to third nanosheets N1, N2, and N3), which overlap eachother in a vertical direction (Z direction) on the fin top surface FT ofthe fin-type active region FA. The first to third nanosheets N1, N2, andN3 may have different respective distances (i.e., Z-directionaldistances) from the fin top surfaces FT of the fin-type active regionsFA. The first nanosheet N1, the second nanosheet N2, and the thirdnanosheet N3 may be sequentially stacked on the fin top surface FT ofthe fin-type active region Fain in this stated order.

Although FIG. 1 illustrates an example in which a planar shape of thenanosheet stack NSS has a substantially tetragonal shape, embodiments ofthe inventive concept are not limited thereto. The nanosheet stack NSSmay have various planar shapes according to a planar shape of thefin-type active region FA and a planar shape of each of the gate lines160. The present example illustrates a case in which the plurality ofnanosheet stacks NSS and the plurality of gate lines 160 are formed onone fin-type active region FA and the plurality of nanosheet stacks NSSmay be located on one fin-type active region FA in a row in the firsthorizontal direction (X direction). However, according to someembodiments of the inventive concept, the number of nanosheet stacks NSSlocated on one fin-type active region FA may not be specificallylimited. For example, one nanosheet stack NSS may be formed on onefin-type active region FA. The present example illustrates a case inwhich each of the plurality of nanosheet stacks NSS includes threenanosheets, but embodiments of the inventive concept are not limitedthereto. For example, the nanosheet stack NSS may include at least twonanosheets, and the number of nanosheets included in the nanosheet stackNSS may not be specifically limited.

Each of the first to third nanosheets N1, N2, and N3 may have a channelregion. In some embodiments, each of the first to third nanosheets N1,N2, and N3 may have a thickness that is selected within a range of about4.5 nm to about 5.5 nm, but embodiments of the inventive concept are notlimited thereto. Here, the thickness of each of the first to thirdnanosheets N1, N2, and N3 may mean a size of each of the first to thirdnanosheets N1, N2, and N3 in the vertical direction (Z direction). Insome embodiments, the first to third nanosheets N1, N2, and N3 may havesubstantially the same thickness. In some other embodiments, at leastsome of the first to third nanosheets N1, N2, and N3 may have differentthicknesses.

At least some of the first to third nanosheets N1, N2, and N3 may havedifferent sizes in the first horizontal direction (X direction). Thefirst nanosheet N1, which is closest to the fin top surface FT in thefirst horizontal direction (X direction), from among the first to thirdnanosheets N1, N2, and N3, may have a smallest length LN1. A length ofeach of the second and third nanosheets N2 and N3 may be greater thanthe length LN1 of the first nanosheet N1 in the first horizontaldirection (X direction). In some embodiments, the second and thirdnanosheets N2 and N3 may have substantially the same length.

As described above, the first nanosheet N1 closest to the fin-typeactive region FA, from among the first to third nanosheets N1, N2, andN3, may have the smallest length LN1, and thus, an effective channellength of a channel formed in the first nanosheet N1 may be relativelyreduced. Accordingly, as compared to a case in which the first nanosheetN1 has the same length as the second and third nanosheets N2 and N3, theamount of current flowing through the first nanosheet N1 may beincreased at the same operating voltage. Thus, the thickness and lengthsof the nanosheets N1, N2, and N3 may affect the amount of current flowtherethrough with decreased thickness and increased length resulting inless current flow and increased thickness and reduced length resultingin more current flow.

A plurality of recesses R1 may be formed in upper portions of thefin-type active regions FA, and a plurality of source/drain regions 134may be formed on the plurality of recesses R1. The plurality ofsource/drain regions 134 may include an epitaxially grown semiconductorlayer. For example, the plurality of source/drain regions 134 mayinclude a Group-IV semiconductor, a Group-IV compound semiconductor, ora Group III-V compound semiconductor.

The plurality of source/drain regions 134 may be doped with an n-typedopant or a p-type dopant. In some embodiments, the plurality ofsource/drain regions 134 may include a Si layer or a SiGe layer. In thiscase, the plurality of source/drain regions 134 may be doped with ann-type dopant selected from phosphorus (P), arsenic (As), and/orantimony (Sb) or a p-type dopant selected from boron (B) and/or gallium(Ga). In some other embodiments, the plurality of source/drain regions134 may include an InGaAs layer or an InGaSb layer. In this case, theplurality of source/drain regions 134 may be doped with an n-type dopantselected from silicon (Si), sulfur (S), selenium (Se), and/or tellurium(Te).

In some embodiments, each of the plurality of source/drain regions 134may include a plurality of semiconductor layers having different dopantconcentrations. For example, each of the plurality of source/drainregions 134 may have a dopant concentration decreasing in a directiontoward the fin-type active region FA and the first to third nanosheetsN1, N2, and N3 and may have a dopant concentration increasing in adirection away from the fin-type active region FA and the first to thirdnanosheets N1, N2, and N3. In some embodiments, the dopant concentrationmay monotonically decrease in the direction toward the fin-type activeregion FA and may monotonically increase in the direction away from thefin-type active region FA.

Each of the plurality of source/drain regions 134 may include asource/drain main region 134M, which is located on the recess R1, and asource/drain protruding region 134P, which is integrally connected tothe source/drain main region 134M and protrudes from the source/drainmain region 134M toward the first nanosheet N1. The source/drainprotruding region 134P may be in contact with the first nanosheet N1.The plurality of source/drain regions 134 may face the first to thirdnanosheets N1, N2, and N3 in the first horizontal direction (Xdirection). One source/drain region 134 may include a pair ofsource/drain protruding regions 134P, which respectively protrude inopposite directions toward the first nanosheet N1 of each of a pair ofnanosheet stacks NSS located adjacent to each other on both sides of theone source/drain region 134. The source/drain main region 134M may notoverlap a pair of nanosheet stacks NSS adjacent thereto on both sides ofthe source/drain region 134 in the vertical direction (Z direction) Thesource/drain protruding region 134P may overlap portions of the first tothird nanosheets N1, N2, and N3 included in the nanosheet stack NSS inthe vertical direction (Z direction).

The length LN1 of the first nanosheet N1 may be defined by twosource/drain protruding regions 134P, which are respectively in contactwith both sidewalls of the first nanosheet N1, in the first horizontaldirection (X direction). The length LN1 of the first nanosheet N1 may beless than a maximum length L1 of the nanosheet stack NSS in the firsthorizontal direction (X direction). In some embodiments, a length LP ofthe source/drain protruding region 134P may be less than ½ of the lengthLN1 of the first nanosheet N1. In some embodiments, the length LN1 ofthe first nanosheet N1 may be at least twice the length LP of thesource/drain protruding region 134P, but embodiments of the inventiveconcept are not limited thereto.

The gate line 160 may be located on the fin-type active region FA to atleast partially cover the nanosheet stack NSS and at least partiallysurround each of the first to third nanosheets N1, N2, and N3. Each ofthe plurality of gate lines 160 may include a main gate portion 160M,which at least partially covers a top surface of the nanosheet stack NSSand extends in the second horizontal direction (Y direction), and aplurality of sub-gate portions 160S, which are integrally connected tothe main gate portion 160M and respectively located one by one betweenthe first to third nanosheets N1, N2, and N3 and between the fin-typeactive region FA and the first nanosheet N1. A thickness of each of theplurality of sub-gate portions 160S may be less than a thickness of themain gate portion 160M in the vertical direction (Z direction). Thefirst to third nanosheets N1, N2, and N3 may, some embodiments, becompletely surrounded by the gate line 160 in the Z direction and have agate-all-around (GAA) structure. That is the first to third nanosheetsN1, N2, and N3 are between the main gate portion 160M and the lowermostone in the Z direction relative to the substrate 102 of the plurality ofsub-gate portions 160S.

The gate line 160 may include a metal, a metal nitride, a metal carbide,or a combination thereof. The metal may be selected from titanium (Ti),tungsten (W), ruthenium (Ru), niobium (Nb), molybdenum (Mo), hafnium(Hf), nickel (Ni), cobalt (Co), platinum (Pt), ytterbium (Yb), terbium(Tb), dysprosium (Dy), erbium (Er), and/or palladium (Pd). The metalnitride may be selected from titanium nitride (TiN) and/or tantalumnitride (TaN). The metal carbide may be titanium aluminum carbide(TiAlC).

A gate dielectric film 152 may be between the nanosheet stack NSS andthe gate line 160. In some embodiments, the gate dielectric film 152 mayinclude a stack structure of an interface film and a high-k dielectricfilm. The interface film may include a low-k dielectric material filmhaving a dielectric constant of about 9 or lower, for example, a siliconoxide film, a silicon oxynitride film, or a combination thereof. In someembodiments, the interface film may be omitted. The high-k dielectricfilm may include a material having a higher dielectric constant than asilicon oxide film. For example, the high-k dielectric film may have adielectric constant of about 10 to about 25. The high-k dielectric filmmay include hafnium oxide, but embodiments of the inventive concept arenot limited thereto.

A plurality of nanosheet transistors TR1 may be formed at intersectionsbetween the plurality of fin-type active regions FA and the plurality ofgate lines 160 on the substrate 102. In the plurality of nanosheettransistors TR1, the first nanosheet N1 closest to the first-type activeregion FA, from among the first to third nanosheets N1, N2, and N3, mayhave the shortest length LN1 so that the effective channel length of thechannel formed in the first nanosheet N1, from among the first to thirdnanosheets N1, N2, and N3, may be less than in other nanosheets. Thus, aresistance of the first nanosheet N1 may be relatively reduced and theamount of current flowing through the first nanosheet N1 may beincreased at the same operating voltage. As a result, a deviation in theamount of current flowing through the first to third nanosheets N1, N2,and N3 may be reduced or minimized in a turn-on state of the nanosheettransistor TR1, and, thus, the performance of the IC device 100 may beimproved or optimized in the turn-on state.

In some embodiments, the first to third nanosheets N1, N2, and N3 mayinclude semiconductor layers having the same element. In an example,each of the first to third nanosheets N1, N2, and N3 may include a Silayer. In another example, each of the first to third nanosheets N1, N2,and N3 may include a SiGe layer.

In some other embodiments, the first to third nanosheets N1, N2, and N3may include semiconductor layers including different elements. Forexample, the first nanosheet N1 may include a SiGe layer, and the secondand third nanosheets N2 and N3 may include a Si layer.

In some other embodiments, the first to third nanosheets N1, N2, and N3may include semiconductor layers having different dopant concentrations.

For example, the first to third nanosheets N1, N2, and N3 may includeone semiconductor element selected from Group IV semiconductor elements,such as Si and Ge. In this case, the first nanosheet N1 may include adoped semiconductor layer, and the second and third nanosheets N2 and N3may include an undoped semiconductor layer. In an example, the firstnanosheet N1 may include a silicon layer doped with an n-type dopant ora p-type dopant, and the second and third nanosheets N2 and N3 mayinclude an undoped silicon layer. For example, the first nanosheet N1may be doped with a dopant of the same conductivity type as aconductivity type of the plurality of source/drain regions 134. In anexample, the first nanosheet N1 may include a Si layer doped with ann-type dopant, the second and third nanosheets N2 and N3 may include anundoped Si layer, and the plurality of source/drain regions 134 mayinclude a Si layer doped with an n-type dopant. In another example, thefirst nanosheet N1 may include a Si layer doped with a p-type dopant,the second and third nanosheets N2 and N3 may include an undoped Silayer, and the plurality of source/drain regions 134 may include a SiGelayer doped with a p-type dopant. In the Si layer doped with the n-typedopant, the n-type dopant may include phosphorus (P), arsenic (As),antimony (Sb), or a combination thereof, but embodiments of theinventive concept are not limited thereto. In the Si layer doped withthe p-type dopant and the SiGe layer doped with the p-type dopant, thep-type dopant may include boron (B), gallium (Ga), or a combinationthereof, but embodiments of the inventive concept are not limitedthereto. For example, a dopant concentration of the Si layer may rangefrom about 1×10¹⁸ cm⁻³ to about 1×10²¹ cm⁻³, but embodiments of theinventive concept are not limited thereto.

In some other embodiments, the first to third nanosheets N1, N2, and N3may include a compound semiconductor selected from a Group-IV compoundsemiconductor and a Group III-V compound semiconductor. In this case,the first nanosheet N1 may include a doped compound semiconductor layer,and the second and third nanosheets N2 and N3 may include an undopedcompound semiconductor layer. The Group III-V compound semiconductor maybe a binary, ternary, or quaternary Group III-V compound semiconductorincluding two, three, or four elements selected from Group-III andGroup-V semiconductors. For example, the first to third nanosheets N1,N2, and N3 may be selected from a Group-IV compound semiconductor, suchas silicon germanium (SiGe), silicon carbide (SiC), silicon germaniumcarbide (SiGeC), germanium tin (GeSn), silicon tin (SiSn), and silicongermanium tin (SiGeSn), and a Group III-V compound semiconductor, suchas indium gallium arsenide (InGaAs), indium gallium antimonide (InGaSb),indium arsenide (InAs), indium phosphide (InP), indium arsenide (InAs),gallium arsenide phosphide (GaAsP), and gallium indium phosphide(GaTnP), but embodiments of the inventive concept are not limitedthereto.

In an example, the first to third nanosheets N1, N2, and N3 may includea SiGe layer. In this case, the first nanosheet N1 may include a SiGelayer doped with an n-type or p-type dopant, and the second and thirdnanosheets N2 and N3 may include an undoped SiGe layer. A conductivitytype of the doped SiGe layer may be the same as a conductivity type ofthe plurality of source/drain regions 134.

In another example, the first to third nanosheets N1, N2, and N3 mayinclude an InGaAs layer. In this case, the first nanosheet N1 mayinclude an InGaAs layer doped with an n-type or p-type dopant, and thesecond and third nanosheets N2 and N3 may include an undoped InGaAslayer. A conductivity type of the doped InGaAs layer may be the same asthe conductivity type of the plurality of source/drain regions 134.

In another example, the first to third nanosheets N1, N2, and N3 mayinclude an InGaSb layer. In this case, the first nanosheet N1 mayinclude an InGaSb layer doped with an n-type or p-type dopant, and thesecond and third nanosheets N2 and N3 may include an undoped InGaSblayer. A conductivity type of the doped InGaSb layer may be the same asthe conductivity type of the plurality of source/drain regions 134.

As in the above-described example, when the first nanosheet N1 closestto the fin-type active region FA, from among the first to thirdnanosheets N1, N2, and N3, includes a semiconductor layer doped with adopant of the same conductivity type as the conductivity type of theplurality of source/drain regions 134 and the second and thirdnanosheets N2 and N3 include an undoped semiconductor layer, in aturn-on state of the nanosheet transistor TR1, the first nanosheet N1may form a junctionless channel and the second and third nanosheets N2and N3 may form p-n junction-based channels. As used herein, the term“junctionless” refers to the absence of a doped p-n junction in achannel at a boundary of the nanosheet transistor TR1. The junctionlesschannel may include a region having a relatively high dopantconcentration and a region having a relatively low dopant concentration,which have the same conductivity type. Only the first nanosheet N1closest to the fin-type active region FA, from among the first to thirdnanosheets N1, N2, and N3, may form the junctionless channel in theturn-on state of the nanosheet transistor TR1, and, thus, the amount ofcurrent flowing through the first nanosheet N1 may be increased.

In some other embodiments, the first to third nanosheets N1, N2, and N3may include the same Group-IV compound semiconductor layer. In thiscase, at least some of the first to third nanosheets N1, N2, and N3 mayinclude Group-IV compound semiconductor layers having differentcompositions. In an example, the first to third nanosheets N1, N2, andN3 may include Si_(1-x)Ge_(x) (0<x<1). In this case, a Ge content ratio(value of x) of the first nanosheet N1, from among the first to thirdnanosheets N1, N2, and N3, may be higher than Ge content ratios (valuesof x) of nanosheets other than the first nanosheet N1. In anotherexample, the first to third nanosheets N1, N2, and N3 may includeSi_(1-x)Ge_(x) (0<x<1). In this case, the Ge content ratio (value of x)may gradually increase in a direction toward the fin-type active regionFA. For example, the first nanosheet N1 may include Si_(0.55)Ge_(0.45),the second nanosheet N2 may include Si_(0.65)Ge_(0.35), and the thirdnanosheet N3 may include Si_(0.75)Ge_(0.25), but embodiments of theinventive concept are not limited thereto. As described above, becausethe first nanosheet N1, which is closest to the fin-type active regionFA, from among the first to third nanosheets N1, N2, and N3, may havethe highest Ge content ratio, a bandgap of the first nanosheet N1 may belower than bandgaps of other nanosheets in the turn-on state of theplurality of nanosheet transistors TR1. Thus, in the turn-on state ofthe nanosheet transistor TR1, the amount of current flowing through thefirst nanosheet N1 closest to the fin-type active region FA, from amongthe first to third nanosheets N1, N2, and N3, may increase. As a result,a deviation in the amount of current flowing through the first to thirdnanosheets N1, N2, and N3 may be reduced or minimized in the turn-onstate of the nanosheet transistor TR1, and, thus, the performance of theIC device 100 may be improved or optimized in the turn-on state.

In some other embodiments, the first to third nanosheets N1, N2, and N3may include the same Group III-V compound semiconductor layer. In thiscase, at least some of the first to third nanosheets N1, N2, and N3 mayinclude a Group III-V compound semiconductor layer having differentcompositions. In an example, the first to third nanosheets N1, N2, andN3 may include In_(1-y)Ga_(y)As (0<y<1). In this case, a Ga contentratio (value of y) of the first nanosheet N1, from among the first tothird nanosheets N1, N2, and N3, may be lower than a Ga content ratio(value of y) of nanosheets other than the first nanosheet N1. Ga contentratios (values of y) of the first to third nanosheets N1, N2, and N3 maybe gradually reduced in a direction toward the fin-type active regionFA, while In content ratios of the first to third nanosheets N1, N2, andN3 may be gradually increased in the direction toward the fin-typeactive region FA. For example, the first nanosheet N1 may includeIn_(0.80)Ga_(0.20)As, the second nanosheet N2 may includeIn_(0.65)Ga_(0.35)As, and the third nanosheet N3 may includeIn_(0.53)Ga_(0.47)As, but embodiments of the inventive concept are notlimited thereto.

In another example, the first to third nanosheets N1, N2, and N3 mayinclude In_(1-z)Ga_(z)Sb (0<z<1). In this case, a Ga content ratio(value of z) of the first nanosheet N1, from among the first to thirdnanosheets N1, N2, and N3, may be lower than Ga content ratios (valuesof z) of nanosheets other than the first nanosheet N1. The Ga contentratios (values of z) of the first to third nanosheets N1, N2, and N3 maybe gradually reduced in the direction toward the fin-type active regionFA. For example, the first nanosheet N1 may includeIn_(0.80)Ga_(0.20)Sb, the second nanosheet N2 may includeIn_(0.65)Ga_(0.35)Sb, and the third nanosheet N3 may includeIn_(0.53)Ga_(0.47)Sb, but embodiments of the inventive concept are notlimited thereto.

As in the above-described example, because the first nanosheet N1, whichis closest to the fin-type active region FA from among the first tothird nanosheets N1, N2, and N3, has the lowest Ga content ratio, abandgap of the first nanosheet N1 may become lower than bandgaps ofother nanosheets in the turn-on state of the plurality of nanosheettransistors TR1. Thus, in the turn-on state of the nanosheet transistorTR1, the amount of current flowing through the first nanosheet N1closest to the fin-type active region FA, from among the first to thirdnanosheets N1, N2, and N3, may increase. As a result, a deviation in theamount of current flowing through the first to third nanosheets N1, N2,and N3 may be reduced or minimized in the turn-on state of the nanosheettransistor TR1, and, thus, the performance of the IC device 100 may beimproved or optimized in the turn-on state.

A metal silicide film 182 may be formed on a top surface of each of theplurality of source/drain regions 134. The metal silicide film 182 mayinclude titanium silicide, but embodiments of the inventive concept arenot limited thereto. The metal silicide film 182 may be omitted.

Both sidewalls of each of the plurality of gate lines 160 may be atleast partially covered by a plurality of outer insulating spacers 118.The plurality of outer insulating spacers 118 may at least partiallycover both sidewalls of the main gate portions 160M on the plurality ofnanosheet stacks NSS. The plurality of outer insulating spacers 118 andthe plurality of source/drain regions 134 may be at least partiallycovered by a protective insulating film 142. Each of the outerinsulating spacers 118 and the protective insulating film 142 mayinclude silicon nitride (SiN), silicon carbonitride (SiCN), siliconboron nitride (SiBN), silicon oxynitride (SiON), silicon oxycarbonitride(SiOCN), silicon boron carbonitride (SiBCN), silicon oxycarbide (SiOC),silicon dioxide (SiO₂), or a combination thereof. The protectiveinsulating film 142 may be omitted in some embodiments.

A plurality of inner insulating spacers 120 may be between the first tothird nanosheets N1, N2, and N3 and between the fin-type active regionFA and the first nanosheet N1. Both sidewalls of each of the pluralityof sub-gate portions 160S may be at least partially covered by the innerinsulating spacers 120 with the gate dielectric film 152 therebetween.The plurality of inner insulating spacers 120 may be between theplurality of sub-gate portions 160S and the plurality of source/drainmain regions 134M and overlap the source/drain protruding regions 134Pin the vertical direction (Z direction). The source/drain protrudingregion 134P may be in contact with the first nanosheet N1 and define alength of the first nanosheet N1 in the first horizontal direction (Xdirection). In the first horizontal direction (X direction), the maximumlength L1 of the nanosheet stack NSS may be substantially equal to adistance 120L between both outermost sidewalls of the inner insulatingspacers 120 located on both sides of each of the plurality of sub-gateportions 160S of the gate line 160.

In some embodiments, the outer insulating spacers 118 may include thesame material as the inner insulating spacers 120. In some otherembodiments, the outer insulating spacers 118 may include a differentmaterial from the inner insulating spacers 120. The inner insulatingspacers 120 may include SiN, SiCN, SiBN, SiON, SiOCN, SiBCN, SiOC, SiO₂,or a combination thereof. The inner insulating spacers 120 may furtherinclude air gaps.

An inter-gate dielectric film 144 and an interlayer insulating film 174may be sequentially formed on the protective insulating film 142. Eachof the inter-gate dielectric film 144 and the interlayer insulating film174 may include a silicon oxide film.

A plurality of contact plugs 184 may be located inside a plurality ofcontact holes 180 passing through the interlayer insulating film 174,the inter-gate dielectric film 144, and the protective insulating film142. The plurality of contact plugs 184 may be connected to theplurality of source/drain regions 134 through a plurality of metalsilicide films 182. Each of the contact plugs 184 may include a metal, aconductive metal nitride, or a combination thereof. For example, each ofthe contact plugs 184 may include tungsten (W), copper (Cu), aluminum(Al), titanium (Ti), tantalum (Ta), titanium nitride (TiN), tantalumnitride (TaN), an alloy thereof, or a combination thereof.

In the IC device 100, because the first nanosheet N1 closest to thefin-type active region FA, from among the first to third nanosheets N1,N2, and N3, has the shortest length, the effective channel length of thechannel formed in the first nanosheet N1 may be reduced. Accordingly, ascompared to a case in which the first nanosheet N1 has the same lengthas the second and third nanosheets N2 and N3, the amount of currentflowing through the first nanosheet N1 may be increased at the sameoperating voltage. For example, when the first nanosheet N1 includes asemiconductor layer doped with a dopant of the same conductivity type asa conductivity type of the plurality of source/drain regions 134, onlythe first nanosheet N1, from among the first to third nanosheets N1, N2,and N3, may be configured to selectively form the junctionless channelin the turn-on state of the nanosheet transistor TR1, and, thus, theamount of current flowing through the first nanosheet N1 may beincreased. In addition, when the first to third nanosheets N1, N2, andN3 include a compound semiconductor layer including Ge or Ga, from amongthe first to third nanosheets N1, N2, and N3, the first nanosheet N1 maybe controlled to have a highest Ge content ratio or a lowest Ga contentratio. Thus, a bandgap of the first nanosheet N1 may be controlled to belower than bandgaps of other nanosheets in the turn-on state of theplurality of nanosheet transistors TR1, and, thus, the amount of currentflowing through the first nanosheet N1 may be increased. As a result, adeviation in the amount of current flowing through the first to thirdnanosheets N1, N2, and N3 may be reduced or minimized in the turn-onstate of the nanosheet transistor TR1, and, thus, the performance of theIC device 100 in the turn-on state may be improved or optimized.

FIG. 3 is a cross-sectional view of an IC device 200 according to someembodiments of the inventive concept, which is an enlargedcross-sectional view of a region corresponding to the partial region X1in FIG. 2A.

Referring to FIG. 3, the IC device 200 may have substantially the sameconfiguration as the IC device 100 described with reference to FIGS. 1,2A, and 2B. However, the IC device 200 may include a plurality ofnanosheet stacks NSS2 facing fin top surfaces FT of a plurality offin-type active regions FA. The plurality of nanosheet stacks NSS2 mayinclude a first nanosheet N21, a second nanosheet N22, and a thirdnanosheet N23, which are sequentially stacked on the fin top surface FTof the fin-type active region FA. A greatest length L2 of each of theplurality of nanosheet stacks NSS2 in a first horizontal direction (Xdirection) may be less than a distance 120L between both outermostsidewalls of inner insulating spacers 120 located on both sides of eachof a plurality of sub-gate portions 160S of a gate line 160.

The first nanosheet N21, which is closest to the fin top surface FT fromamong the first to third nanosheets N21, N22, and N23, may have ashortest length in the first horizontal direction (X direction), and thesecond and third nanosheets N22 and N23 may have substantially the samelength.

The IC device 200 may include a plurality of source/drain regions 234.Each of the plurality of source/drain regions 234 may include asource/drain main region 234M, which is located on a recess R1, andfirst to third source/drain protruding regions 234P1, 234P2, and 234P3,which are integrally connected to the source/drain main region 234M andprotrude from the source/drain main region 234M toward the first tothird nanosheets N21, N22, and N23. The first to third source/drainprotruding regions 234P1, 234P2, and 234P3 may be in physical contactwith the first to third nanosheets N21, N22, and N23, respectively. Onesource/drain region 234 may include a pair of first source/drainprotruding regions 234P1, a pair of second source/drain protrudingregions 234P2, and a pair of third source/drain protruding regions234P3. The pair of first source/drain protruding regions 234P1 mayprotrude in opposite directions toward the first nanosheet N21 of eachof a pair of nanosheet stacks NSS2 located adjacent to each other onboth sides of a source/drain region 234. The pair of second source/drainprotruding regions 234P2 may protrude in opposite directions toward thesecond nanosheet N22 of each of the pair of nanosheet stacks NSS2. Thepair of third source/drain protruding regions 234P3 may protrude inopposite directions toward the third nanosheet N23 of each of the pairof nanosheet stacks NSS2. In the first horizontal direction (Xdirection), lengths LP22 of the second and third source/drain protrudingregions 234P2 and 234P3 may be substantially equal or similar and beless than a length LP21 of the first source/drain protruding region234P1.

Detailed configurations and effects of the plurality of nanosheet stacksNSS2 and the plurality of source/drain regions 234 may be the same as orsimilar to those of the plurality of nanosheet stacks NSS and theplurality of source/drain regions 134 described with reference to FIGS.1, 2A, and 2B.

FIG. 4 is a cross-sectional view of an IC device 300 according to someembodiments of the inventive concept, which is an enlargedcross-sectional view of a region corresponding to the partial region X1in FIG. 2A.

Referring to FIG. 4, the IC device 300 may have substantially the sameconfiguration as the IC device 100 described with reference to FIGS. 1,2A, and 2B. However, the IC device 300 may include a plurality ofnanosheet stacks NSS3 facing fin top surfaces FT of a plurality offin-type active regions FA. The plurality of nanosheet stacks NSS3 mayinclude a first nanosheet N31, a second nanosheet N32, and a thirdnanosheet N33, which are sequentially stacked on the fin top surface FTof the fin-type active region FA. In a first horizontal direction (Xdirection), a greatest length L3 of the plurality of nanosheet stacksNSS3 may be less than a distance 120L between both outermost sidewallsof inner insulating spacers 120 located on both sides of each of aplurality of sub-gate portions 160S of a gate line 160.

The first to third nanosheets N31, N32, and N33 may have differentlengths in the horizontal direction (X direction). The first nanosheetN31, which is closest to the fin top surface FT from among the first tothird nanosheets N31, N32, and N33, may have a shortest length, andlengths of the second and third nanosheets N32 and N33 may increase in adirection away from the fin top surface FT.

The IC device 300 may include a plurality of source/drain regions 334.Each of the plurality of source/drain regions 334 may include asource/drain main region 334M, which is located on a recess R1, andfirst to third source/drain protruding regions 334P1, 334P2, and 334P3,which are integrally connected to the source/drain main region 334M andprotrude from the source/drain main region 334M toward the first tothird nanosheets N31, N32, and N33. The first to third source/drainprotruding regions 334P1, 334P2, and 334P3 may be in physical contactwith the first to third nanosheets N21, N22, and N23, respectively. Inthe first horizontal direction (X direction), from among the first tothird source/drain protruding regions 334P1, 334P2, and 334P3, the firstsource/drain protruding region 334P1 may have a shortest length, and thesecond and third source/drain protruding regions 334P2 and 334P3 mayhave reduced lengths in a direction away from the fin top surface FT.

One source/drain region 334 may include a pair of first source/drainprotruding regions 334P1, a pair of second source/drain protrudingregions 334P2, and a pair of third source/drain protruding regions334P3. The pair of first source/drain protruding regions 334P1 mayprotrude in opposite directions toward the first nanosheet N31 of eachof a pair of nanosheet stacks NSS3 adjacent to each other on both sidesof a source/drain region 334. The pair of second source/drain protrudingregions 334P2 may protrude in opposite directions toward the secondnanosheet N32 of each of the pair of nanosheet stacks NSS3. The pair ofthird source/drain protruding regions 334P3 may protrude in oppositedirections toward the third nanosheet N33 of each of the pair ofnanosheet stacks NSS3. In the first horizontal direction (X direction),lengths LP31, LP32, and LP33 of the first to third source/drainprotruding regions 334P1, 334P2, and 334P3 may be reduced in a directionaway from the fin top surface FT, and the length LP31 of the firstsource/drain protruding region 334P1 may be the longest.

Although FIG. 4 illustrates an example in which the length of the secondnanosheet N32 is less than the length of the third nanosheet N33 in thefirst horizontal direction (X direction), the inventive concept is notlimited thereto. For example, the length of the third nanosheet N33 maybe less than the length of the second nanosheet N32. In this case, thelength LP32 of the second source/drain protruding region 334P2 may beless than the length LP33 of the third source/drain protruding region334P3.

Detailed configurations and effects of the plurality of nanosheet stacksNSS3 and the plurality of source/drain regions 334 may be the same as orsimilar to those of the plurality of nanosheet stacks NSS and theplurality of source/drain regions 134 described with reference to FIGS.1, 2A, and 2B.

FIGS. 5A to 5Q are cross-sectional views illustrating a process sequenceof a method of manufacturing an IC device 100 according to someembodiments of the inventive concept. A method of manufacturing the ICdevice 100 described with reference to FIGS. 1, 2A, and 2B, according toan example embodiment, will be described with reference to FIGS. 5A to5Q. FIGS. 5A to 5Q illustrate cross-sectional configurations of aportion corresponding to a cross-section taken along the line X-X′ ofFIG. 1, according to the process sequence. In FIGS. 5A to 5Q, the samereference numerals are used to denote the same elements as in FIGS. 1,2A, and 2B, and detailed descriptions thereof will be omitted.

Referring to FIG. 5A, a plurality of sacrificial semiconductor layers104 and a plurality of nanosheet semiconductor layers NS may bealternately stacked on a substrate 102.

The plurality of sacrificial semiconductor layers 104 and the pluralityof nanosheet semiconductor layers NS may include semiconductor materialshaving different etch selectivities. In some embodiments, the pluralityof nanosheet semiconductor layers NS may include silicon (Si), and theplurality of sacrificial semiconductor layers 104 may include silicongermanium (SiGe). In some other embodiments, the plurality of nanosheetsemiconductor layers NS may include silicon germanium, and the pluralityof sacrificial semiconductor layers 104 may include silicon orgermanium. In some other embodiments, the plurality of nanosheetsemiconductor layers NS may include indium gallium arsenide (InGaAs) orindium gallium antimonide (InGaSb), and the plurality of sacrificialsemiconductor layers 104 may include indium phosphide (InP).

Referring to FIG. 5B, a mask pattern MP may be formed on a stackstructure of the plurality of sacrificial semiconductor layers 104 andthe plurality of nanosheet semiconductor layers NS. The plurality ofsacrificial semiconductor layers 104, the plurality of nanosheetsemiconductor layers NS, and the substrate 102 may be partially etchedusing the mask pattern MP as an etch mask to form a trench T1. As aresult, a fin-type active region FA may be defined by the trench T1, thestack structure of the plurality of sacrificial semiconductor layers 104and the plurality of nanosheet semiconductor layer NS may remain on afin top surface FT of the fin-type active region FA.

The mask pattern MP and the fin-type active region FA may include linepatterns extending lengthwise in an X direction. The mask pattern MP mayinclude a pad oxide film pattern 512 and a hard mask pattern 514. Thehard mask pattern 514 may include silicon nitride, polysilicon, aspin-on hardmask (SOH) material, or a combination thereof. The SOHmaterial may include a hydrocarbon compound at a relatively high carboncontent of about 85% to 99% by weight, based on the total weight of theSOH material.

Referring to FIG. 5C, a device isolation film 114 may be formed insidethe trench T1.

Referring to FIG. 5D, the mask pattern MP may be removed from theresultant structure of FIG. 5C and the device isolation film 114 may bepartially removed so that a top surface of the device isolation film 114may be at substantially the same level as or a similar level to the fintop surface FT of the fin-type active region FA.

Referring to FIG. 5E, a plurality of dummy gate structures DGS may beformed on the stack structure of the plurality of sacrificialsemiconductor layers 104 and the plurality of nanosheet semiconductorlayers NS, which remain on the fin-type active region FA.

Each of the plurality of dummy gate structures DGS may extend in adirection that intersects with the fin-type active region FA. Each ofthe plurality of dummy gate structures DGS may have a structure in whichan oxide film D112, a dummy gate layer D114, and a capping layer D116are sequentially stacked. In some embodiments, the dummy gate layer D114may include polysilicon, and the capping layer D116 may include asilicon nitride film.

Referring to FIG. 5F, a plurality of outer insulating spacers 118 may berespectively formed to cover both sidewalls of the plurality of dummygate structures DGS. Thereafter, the plurality of sacrificialsemiconductor layers 104 and the plurality of nanosheet semiconductorlayers NS may be partially removed using the plurality of dummy gatestructures DGS and the plurality of outer insulating spacers 118 as etchmasks so that the plurality of nanosheet semiconductor layers NS may bedivided into a plurality of nanosheet stacks NSS including a pluralityof nanosheets (e.g., first to third nanosheets N1, N2, and N3).Afterwards, the fin-type active region FA, which is exposed between therespective nanosheet stacks NSS, may be etched to form recesses R1 in anupper portion of the fin-type active region FA. To form a plurality ofrecesses R1, the fin-type active region FA may be etched using a dryetching process, a wet etching process, or a combination thereof.

Referring to FIG. 5G, the plurality of sacrificial semiconductor layers104, which are exposed on both sides of the plurality of nanosheetstacks NSS through the plurality of recesses R1, may be partiallyremoved to form a plurality of sacrificial indent regions 104D among thefirst to third nanosheets N1, N2, and N3 and between the first nanosheetN1 and the fin top surface FT of the fin-type active region FA.

To form the plurality of sacrificial indent regions 104D, portions ofthe plurality of sacrificial semiconductor layers 104 may be selectivelyetched using an etch selectivity between the plurality of sacrificialsemiconductor layers 104 and the first to third nanosheets N1, N2, andN3.

Referring to FIG. 5H, a plurality of inner insulating spacers 120 may beformed to at least partially fill the plurality of sacrificial indentregions 104D (refer to FIG. 5G). To form the plurality of innerinsulating spacers 120, an atomic layer deposition (ALD) process, achemical vapor deposition (CVD) process, an oxidation process, or acombination thereof may be used.

Referring to FIG. 5I, from among the first to third nanosheets N1, N2,and N3, which are exposed on both sides of each of the plurality ofnanosheet stacks NSS through the plurality of recesses R1, the firstnanosheet N1 closest to the fin top surface FT may be partially removed,so that a length of the first nanosheet N1 may be reduced, and firstnanosheet indent regions ND1 may be formed on both sides of the firstnanosheet N1 and communicate with the recesses R1.

After the first nanosheet indent regions ND1 are formed, a length LN1 ofthe first nanosheet N1 may be less than a greatest length L1 of thenanosheet stack NSS in a first horizontal direction (X direction).

In some embodiments, the first nanosheet indent regions ND1 may beformed using an isotropic etching process. To form the first nanosheetindent regions ND1, only the doped first nanosheet N1 of the first tothird nanosheets N1, N2, and N3 may be selectively etched using anetching atmosphere having an etch selectivity based on materialsincluded in the first to third nanosheets N1, N2, and N3, and/or usingan etching atmosphere having an etch selectivity based on whether thefirst to third nanosheets N1, N2, and N3 are doped.

In an example, when the first nanosheet N1 includes a doped Si layer andthe second and third nanosheets N2 and N3 include an undoped Si layer,the first nanosheet indent region ND1 may be formed by selectivelyetching only the doped first nanosheet N1, from among the first to thirdnanosheets N1, N2, and N3, through vacant spaces on the plurality ofrecesses R1 in a first etching atmosphere using a difference in etchrate based on whether the Si layer is doped. The first etchingatmosphere may include a liquid or gaseous etchant. For example, thefirst etching atmosphere may include a mixture of HF and HNO₃, a mixtureof HF, HNO₃, and acetic acid (CH₃COOH), an aqueous solution containingHF and isopropyl alcohol, an aqueous solution containing HF and HCl, aKOH aqueous solution, tetramethyl ammonium hydroxide (TMAH), and/orethylene diamine pyrochatechol (EDP), but embodiments of the inventiveconcept are not limited thereto.

In another example, when the first nanosheet N1 includes a SiGe layerand the second and third nanosheets N2 and N3 include a Si layer, thefirst nanosheet indent regions ND1 may be formed by selectively etchingonly the doped first nanosheet N1, from among the first to thirdnanosheets N1, N2, and N3, through vacant spaces on the plurality ofrecesses R1 in a second etching atmosphere using a difference in etchrate between SiGe and Si. The second etching atmosphere may include aliquid or gaseous etchant. For example, the second etching atmospheremay include a CH₃COOH-based etchant, for example, a mixture of HNO₃, HF,and CH₃COOH, but the inventive concept is not limited thereto.

Referring to FIG. 5J, a plurality of source/drain regions 134 may beformed on the fin-type active region FA on both sides of the pluralityof nanosheet stacks NSS. Each of the plurality of source/drain regions134 may include a source/drain main region 134M, which is located on therecess R1, and a source/drain protruding region 134P, which isintegrally connected to the source/drain main region 134M and protrudesfrom the source/drain main region 134M toward the first nanosheet N1 toat least partially fill the first nanosheet indent region ND1.

To form the plurality of source/drain regions 134, a semiconductormaterial may be epitaxially grown from surfaces of the recesses R1 andboth sidewalls of the first nanosheet N1, which are exposed through thefirst nanosheet indent regions ND1.

In some embodiments, to form the plurality of source/drain regions 134,a low-pressure chemical vapor deposition (LPCVD) process, a selectiveepitaxial growth (SEG) process, or a cyclic deposition and etching (CDE)process may be performed using a precursor including a semiconductorelement precursor. The semiconductor element precursor may include anelement, such as silicon (Si), germanium (Ge), indium (In), gallium(Ga), arsenic (As), and antimony (Sb).

In an example, the plurality of source/drain regions 134 includingsilicon may be formed by using a Si-containing compound (e.g., silane(SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), and dichlorosilane(SiH₂Cl₂)) as a silicon source. In another example, the plurality ofsource/drain regions 134 including SiGe may be formed by further using agas mixture of a Ge-containing gas (e.g., germane (GeH₄)) and H₂ inaddition to the silicon source. A dopant ion implantation process may beperformed in-situ with the epitaxial growth process for forming theplurality of source/drain regions 134.

In some embodiments, when the first to third nanosheets N1, N2, and N3include Si, Ge, and/or SiGe, the plurality of source/drain regions 134may include a Si layer, a SiGe layer, and/or a SiC layer. In some otherembodiments, when the first to third nanosheets N1, N2, and N3 includeInGaAs, the plurality of source/drain regions 134 may include InGaAsand/or InAs. When the first to third nanosheets N1, N2, and N3 includeInGaSb, the plurality of source/drain regions 134 may include InGaSb.

In some embodiments, each of the plurality of source/drain regions 134may be formed to include a plurality of semiconductor layers havingdifferent dopant concentrations. For example, each of the plurality ofsource/drain regions 134 may be formed to have a dopant concentrationdecreasing in a direction toward the fin-type active region FA and thefirst to third nanosheets N1, N2, and N3 and have a dopant concentrationincreasing in a direction away from the fin-type active region FA andthe first to third nanosheets N1, N2, and N3. In some embodiments, thedopant concentration may monotonically decrease in the direction towardthe fin-type active region FA and may monotonically increase in thedirection away from the fin-type active region FA.

Referring to FIG. 5K, a protective insulating film 142 may be formed toat least partially cover the resultant structure having the plurality ofsource/drain regions 134. An inter-gate dielectric film 144 may beformed on the protective insulating film 142, and the protectiveinsulating film 142 and the inter-gate dielectric film 144 may beplanarized to expose a top surface of the capping layer D116.

Referring to FIG. 5L, the capping layer D116 may be removed from theresultant structure of FIG. 5K to expose the dummy gate layer D114.Thereafter, the protective insulating film 142 and the inter-gatedielectric film 144 may be partially removed so that a top surface ofthe inter-gate dielectric film 144 may be at substantially the samelevel as a top surface of the dummy gate layer D114.

Referring to FIG. 5M, the dummy gate layer D114 and the oxide film D112located thereunder may be removed from the resultant structure of FIG.5L to prepare gate spaces GS, and the plurality of nanosheet stacks NSSmay be exposed through the gate spaces GS. Thereafter, the plurality ofsacrificial semiconductor layers 104 remaining on the fin-type activeregion FA may be removed through the gate spaces GS so that the gatespaces GS may be extended to spaces between the first to thirdnanosheets N1, N2, and N3 and a space between the first nanosheet N1 andthe fin top surface FT.

Referring to FIG. 5N, a gate dielectric film 152 may be formed to atleast partially cover exposed surfaces of the first to third nanosheetsN1, N2, and N3 and the fin-type active region FA. The gate dielectricfilm 152 may be formed using an ALD process.

Referring to FIG. 5O, a gate-forming conductive layer 160L may be formedon the gate dielectric film 152 to at least partially fill the gatespaces GS (refer to FIG. 5N) and cover the top surface of the inter-gatedielectric film 144. The gate-forming conductive layer 160L may includea metal, a metal nitride, a metal carbide, or a combination thereof. Thegate-forming conductive layer 160L may be formed using an ALD process.

Referring to FIG. 5P, the gate-forming conductive layer 160L and thegate dielectric film 152 may be at least partially removed from the topsurface of the inter-gate dielectric film 144 to expose the top surfaceof the inter-gate dielectric film 144 in the resultant structure of FIG.5O. As a result, a plurality of gate lines 160 may be formed to fill aplurality of gate spaces GS. Each of the plurality of gate lines 160 mayinclude a main gate portion 160M and a plurality of sub-gate portions160S. A planarization process may be performed during the formation ofthe plurality of gate lines 160; as a result, a height of each of theplurality of outer insulating spacers 118, the protective insulatingfilm 142, and the inter-gate dielectric film 144 may be reduced.

Referring to FIG. 5Q, an interlayer insulating film 174 may be formed toat least partially cover the plurality of gate lines 160. Thereafter,the interlayer insulating film 174, the inter-gate dielectric film 144,and the protective insulating film 142 may be partially etched to form aplurality of contact holes 180 exposing the plurality of source/drainregions 134. A metal silicide film 182 may be formed on a top surface ofeach of the plurality of source/drain regions 134 exposed through theplurality of contact holes 180. Contact plugs 184 may be formed on themetal silicide film 182 to at least partially fill the contact holes180. As a result, the IC device 100 shown in FIGS. 1, 2A, and 2B may beformed.

According to the method of manufacturing the IC device 100, whichembodiments are described with reference to FIGS. 5A to 5Q, the ICdevice 100 in which the first nanosheet N1 closest to the fin topsurface FT of the fin-type active region FA, from among the first tothird nanosheets N1, N2, and N3 included in the nanosheet stack NSS, hasa smallest length in the first horizontal direction (X direction) can bemanufactured using a relatively simple method at relatively lowmanufacturing costs. Accordingly, even if a lower portion of each of theplurality of source/drain regions 134 has a higher resistance than anupper portion thereof because each of the plurality of source/drainregions 134 has a higher dopant concentration in upper verticaldirection (Z direction) away from the substrate 102 or even if it ishighly likely that the flow of current is concentrated on an uppernanosheet close to the contact plug 184, from among the first to thirdnanosheets N1, N2, and N3, in a turn-on state of the nanosheettransistor TR1, an effective channel length of a channel formed in thefirst nanosheet N1, which is close to a lower portion of thesource/drain region 134 having a relatively high resistance and locatedfarthest from the contact plug 184, may be reduced to reduce aresistance of the first nanosheet N1. Therefore, the amount of currentflowing through the first nanosheet N1 may be increased at the sameoperating voltage. As a result, a deviation in the amount of currentflowing through the first to third nanosheets N1, N2, and N3 may bereduced or minimized in a turn-on state of the nanosheet transistor TR1,and, thus, the performance of the IC device 100 may be improved oroptimized in the turn-on state.

While methods of manufacturing the IC device 100 shown in FIGS. 1, 2A,and 2B, according to the example embodiments of the inventive concept,have been described above with reference to FIGS. 5A to 5Q, it will beunderstood that various changes and modifications in form and detailsmay be made therein without departing from the spirit and scope of theinventive concept and IC devices having variously changed and modifiedstructures may be manufactured from the descriptions presented withreference to FIGS. 5A to 5Q. For example, to manufacture the IC devices200 and 300 shown in FIGS. 3 and 4, methods described with reference toFIGS. 5A to 5Q may be used. For example, portions of sidewalls of eachof the first to third nanosheets N1, N2, and N3 exposed in an upperportion of the recess R1 may be etched using a similar method to themethod of forming the first nanosheet indent region ND1 with referenceto FIG. 5I and, thus, a plurality of indent regions, which may containthe first to third source/drain protruding regions 234P1, 234P2, and234P3 shown in FIG. 3, or a plurality of indent regions, which maycontain the first to third source/drain protruding regions 334P1, 334P2,and 334P3 shown in FIG. 4, may be formed. To this end, a type and acomposition of an etchant included in an isotropic etching atmosphere, atemperature of an etching atmosphere, and the like may be adjustedaccording to a length to be removed from the sidewalls of each of thefirst to third nanosheets N1, N2, and N3 to control a desired etchingamount of each of the first to third nanosheets N1, N2, and N3.

While the inventive concept has been particularly shown and describedwith reference to embodiments thereof, it will be understood thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

What is claimed is:
 1. An integrated circuit device comprising: afin-type active region extending lengthwise in a first direction; aplurality of nanosheets overlapping each other in a second direction onthe fin-type active region, each of the plurality of nanosheetscomprising a compound semiconductor layer; and a source/drain region onthe fin-type active region, wherein the plurality of nanosheetscomprises a first nanosheet, which is closest to the fin-type activeregion, the first nanosheet having a shortest length in the firstdirection from among the plurality of nanosheets, and wherein acomposition of the compound semiconductor layer in the first nanosheetis different from a composition of the compound semiconductor layer inothers of the plurality of nanosheets.
 2. The integrated circuit deviceof claim 1, wherein the source/drain region comprises a source/drainmain region and a source/drain protruding region protruding from thesource/drain main region, and wherein the source/drain protruding regionprotrudes from the source/drain main region toward the first nanosheetto overlap portions of the plurality of nanosheets in the seconddirection.
 3. The integrated circuit device of claim 1, wherein thefirst nanosheet includes a doped compound semiconductor layer, and theothers of the plurality of nanosheets include an undoped compoundsemiconductor layer.
 4. The integrated circuit device of claim 1,wherein the compound semiconductor layer includes a compoundsemiconductor selected from silicon germanium (SiGe), silicon carbide(SiC), silicon germanium carbide (SiGeC), germanium tin (GeSn), silicontin (SiSn), and silicon germanium tin (SiGeSn).
 5. The integratedcircuit device of claim 1, wherein the compound semiconductor layerincludes a compound semiconductor selected from indium gallium arsenide(InGaAs), indium gallium antimonide (InGaSb), indium arsenide (InAs),indium phosphide (InP), indium arsenide (InAs), gallium arsenidephosphide (GaAsP), and gallium indium phosphide (GaInP).
 6. Theintegrated circuit device of claim 1, wherein the first nanosheetincludes a doped compound semiconductor layer, and the first nanosheetand the source/drain region have a same dopant conductivity type.
 7. Theintegrated circuit device of claim 1, wherein each of the plurality ofnanosheets includes Si_(1-x)Ge_(x) (0<x<1), and wherein a Ge contentratio of the first nanosheet is different from a Ge content ratio of theothers of the plurality of nanosheets.
 8. The integrated circuit deviceof claim 1, wherein each of the plurality of nanosheets includesSi_(1-x)Ge_(x) (0<x<1), and wherein a Ge content ratio of the firstnanosheet is higher than a Ge content ratio of the others of theplurality of nanosheets.
 9. The integrated circuit device of claim 1,wherein each of the plurality of nanosheets includes Si_(1-x)Ge_(x)(0<x<1), and wherein a Ge content ratio in the plurality of nanosheetsgradually increases in a direction toward the fin-type active region.10. The integrated circuit device of claim 1, wherein each of theplurality of nanosheets includes In_(1-y)Ga_(y)As (0<y<1), and wherein aGa content ratio of the first nanosheet is different from a Ga contentratio of the others of the plurality of nanosheets other than the firstnanosheet.
 11. The integrated circuit device of claim 1, wherein each ofthe plurality of nanosheets includes In_(1-y)Ga_(y)As (0<y<1), andwherein an In content ratio of the first nanosheet is different from anIn content ratio of the others of the plurality of nanosheets.
 12. Theintegrated circuit device of claim 1, wherein each of the plurality ofnanosheets includes In_(1-z)Ga_(z)Sb (0<z<1), and wherein a Ga contentratio of the first nanosheet is different from a Ga content ratio of theothers of the plurality of nanosheets.
 13. An integrated circuit devicecomprising: a fin-type active region extending lengthwise in a firstdirection; a plurality of nanosheets overlapping each other in a seconddirection on the fin-type active region, each of the plurality ofnanosheets comprising a compound semiconductor layer; a gate structurecomprising a main gate portion extending in a third direction planarwith and intersecting the first direction on the plurality of nanosheetsand a plurality of sub-gate portions connected to the main gate portion,the plurality of sub-gate portions being interleaved with the pluralityof nanosheets on the fin-type active region; and a pair of source/drainregions on the fin-type active region, the plurality of nanosheets andthe gate structure being interposed between the pair of source/drainregions, wherein the plurality of nanosheets comprises a firstnanosheet, a second nanosheet, and a third nanosheet, which aresequentially stacked on the fin-type active region, the first nanosheetbeing closest to the fin-type active region and having a shortest lengthin the first direction from among the plurality of nanosheets, andwherein a composition of the compound semiconductor layer in the firstnanosheet is different from a composition of each of the compoundsemiconductor layer in the second nanosheet and the third nanosheet. 14.The integrated circuit device of claim 13, wherein the first nanosheetincludes a doped compound semiconductor layer, and each of the secondnanosheet and the third nanosheet includes an undoped compoundsemiconductor layer.
 15. The integrated circuit device of claim 13,wherein each of the plurality of nanosheets includes Si_(1-x)Ge_(x)(0<x<1), and wherein a Ge content ratio of the first nanosheet isdifferent from a Ge content ratio of each of the second nanosheet andthe third nanosheet.
 16. The integrated circuit device of claim 13,wherein each of the plurality of nanosheets includes In_(1-y)Ga_(y)As(0<y<1) or In_(1-z)Ga_(z)Sb (0<z<1), and wherein a Ga content ratio ofthe first nanosheet is different from a Ga content ratio of each of thesecond nanosheet and the third nanosheet.
 17. An integrated circuitdevice comprising: a fin-type active region extending lengthwise in afirst direction; a plurality of nanosheets overlapping each other in asecond direction on the fin-type active region; and a pair ofsource/drain regions on the fin-type active region, each of the pair ofsource/drain regions comprising at least one source/drain protrudingregion protruding toward the plurality of nanosheets, wherein theplurality of nanosheets comprises a first nanosheet, a second nanosheet,and a third nanosheet, the first nanosheet being closest to the fin-typeactive region and having a shortest length in the first direction fromamong the plurality of nanosheets, the second nanosheet and the thirdnanosheet having a same length in the first direction, and wherein acomposition of the compound semiconductor layer in the first nanosheetis different from a composition of each of the compound semiconductorlayer in the second nanosheet and the third nanosheet.
 18. Theintegrated circuit device of claim 17, wherein the first nanosheet andthe pair of source/drain regions have a same dopant conductivity type.19. The integrated circuit device of claim 17, wherein each of theplurality of nanosheets comprises silicon germanium (SiGe), and whereina Ge content ratio of the first nanosheet is greater than respective Gecontent ratios of the second nanosheet and the third nanosheet.
 20. Theintegrated circuit device of claim 17, wherein each of the plurality ofnanosheets comprises a Group III-V semiconductor compound comprisinggallium (Ga), and wherein a Ga content ratio of the first nanosheet isless than respective Ga content ratios of the second nanosheet and thethird nanosheet.